Abstract
All of 17 calves 1 to 21 days old and 23 of 24 1-day-old pigs inoculated orally with calf feces containing cryptosporidia oocysts became infected with cryptosporidia. Infectivity was maintained by discontinuous passage in calves, with storage in potassium dichromate solution for up to eight weeks between passages. Cryptosporidia shed in calf feces also were infectious for calves directly after collection, without storage in potassium dichromate (two calves). Infected calves and pigs shed cryptosporidia oocysts in their feces for several days (mean of 10 days). Those necropsied at this stage of infection had many cryptosporidia and partial atrophy of villi in their ilea. All of the pigs and 60% of the calves also had cryptosporidia infections in their large intestines at this stage. It was concluded that calf cryptosporidia can be transmitted via feces to calves and to pigs.